Floor drains are used across the world to allow quick and easy removal of waste water and debris from tiled or hard surfaced flooring after washing. They are commonly used in showers and in factories where sanitation is extremely important. Floor drains are connected by a pipe to a soil stack or similar sewer.
A positive pressure differential normally exists between the sewer and the surrounding environment, that is the pressure is higher in the sewer than it is in the surrounding environment. Such a situation allows for a flow of air and associated odours from the sewer into the environment surrounding the floor drain and inlet.
It is preferable to provide some form of trap between the floor drain inlet and the soil stack or sewer to prevent the ingress of these odours and also to prevent the ingress of creatures from the sewer into the environment surrounding the floor drain and inlet.
Where a trap is provided, the style of trap typically used is a liquid trap. However, liquid traps can get blocked quite easily if larger objects are brushed into the drain. Floor drains generally have no form of flushing system and are reliant on buckets of water to keep them clean and in the event of blockage, and often require rodding. Additionally, liquid traps, especially in hot countries, can evaporate allowing the ingress of rodents and odours from the sewers into the environment surrounding the drain opening.
Furthermore, in many countries, drainage systems are not vented, and a negative pressure differential can exist, that is the pressure within the sewer is lower than the environmental pressure which applies a downstream pulling force to the liquid trap, with the result that liquid traps can be sucked downstream, removing the trap and exposing the environment to downhole odours and rodents.
Floor drains without traps do not block as easily but have little resistance to odours and rodents from the sewer below, the only protection for the surrounding environment being the provision of a cover, such as a grating.